This invention relates to the field of hand-held power saws and, more particularly, to a viewing window in a circular saw blade guard.
Hand-held power circular saws have been popular woodworking tools for many years. In a typical sawing operation, the user begins by marking or otherwise identifying a desired line along which to saw the material to be cut. The user then guides the saw during cutting, manually aligning the blade with the desired line of cut. Maintaining this alignment manually can be difficult because the typical circular saw has a blade guard that obscures the user's view of the blade at the point of cutting and thus impedes the user's ability to accurately align the blade with the desired cutting line.
To overcome this difficulty, one alternative has been to provide the circular saw with a guide slot. Typically located on the base of the saw, the guide slot is so aligned ahead of the blade in the forward cutting direction to provide a visual indication of the anticipated blade path through the workpiece. During operation, the user typically positions the saw so that the guide slot, and thus the blade, are aligned with the line of cut. This approach can provide a satisfactory cut, unless the saw blade is improperly aligned with the guide slot. A blade is typically oriented at a predesignated location on an arbor driven by the saw motor. Deviations from this orientation can occur causing misalignment between the blade and the guide slot. The guide slot will then incorrectly indicate the blade path, and the user relying on the guide slot will less likely cut the material as desired. Furthermore, since the blade is covered by the saw guard, the user cannot directly monitor the blade travel and, therefore, may not detect the misalignment until substantial cutting has occurred. As a result, the workpiece may be ruined.
To overcome these limitations, another alternative has been to supply the saw guard with a transparent viewing window covering an aperture in the saw guard. Such a window enables direct observation of the saw blade as it enters the workpiece, which in turn enables the user to better maintain a desired cutting path. For example, U.S. Pat. No. 1,830,579 to Wappat provides an observation opening in the side wall of a hand-held circular saw guard. However, the use of a side wall viewing port did not permit the user to saw from a comfortable position behind the saw and at the same time monitor the progress of the blade. Furthermore, to the extent the air currents directed towards the inside surface of the viewing pane were not sufficient to clear the pane of dust, manual clearing of the pane would be required which could more directly expose the saw blade.
A viewing window covering an aperture on the outside circumference of a circular saw blade guard is disclosed in U.S. Pat. No. 4,450,627 to Morimoto. This viewing window is coupled with the saw guard in a variety of ways, including by means of a press fit, a sliding fit or a side hinge. When the viewing window requires cleaning, however, it must either be removed or substantially opened, thereby exposing the saw blade area. After cleaning, if the user neglects to install or close the viewing window, sawing operation without the viewing window in place could occur. The user may not notice the missing viewing window until sawing operations have begun, and cut material could be ejected through the uncovered aperture. The side hinge structure disclosed in this patent allows complete exposure of the aperture in the saw guard.
To overcome these and other limitations in the prior art, an improved viewing window is desirable for a circular saw guard that is easily cleanable without requiring full exposure of the saw guard aperture.